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Tropical plants like papaya (Carica papaya) need warm, steady temperatures throughout the year for the best growth. Both the air and soil temperatures can determine the success or decline of the plant and its fruit production. Before you plant a papaya for fruit, you should know your area's temperatures and how they can affect your papaya tree. The best places for papaya growth are in U.S. Department of Agriculture plant hardiness zones 10 and 11.

When Temperatures Are Perfect

The best air temperatures for papayas range from 70 to 90 degrees Fahrenheit throughout the year. Soil temperatures must always stay above 60 F for best growth. Excessively warm or cold temperatures can negatively affect the tree or its fruit. In cooler USDA zones 8b through 9, papayas may be grown as ornamental plants. The temperatures in these zones allow papayas to grow and flower, but winter frosts and occasional freezes in these areas prevent the trees from fruiting.

When Cold Weather Hits

Papaya grown outdoors require protection when a rare freeze hits. Even a light freeze with temperatures at 32 F can cause severe damage to the plant and overnight freezes may kill unprotected trees. Milder, but still chilly temperatures, below 59 F, prevent the tree from flowering or cause it to produce misshapen fruit. Chilly weather below the ideal minimum air temperatures may also result in fruit with an altered or bland flavor. Reduce watering in cold weather because wet soil and cold weather can kill papaya trees. Protect papaya trees from cold weather with Christmas lights hung on the branches and a blanket held over the tree on a frame.

When the Heat is On

Although papaya trees prefer warm and sunny conditions to produce the sweetest fruit, too much heat can disrupt the plant's fruiting. Weather above 90 F can cause a sudden dropping of flowers and when the flowers fall off the plant, it cannot produce fruit. In long, hot summers, you may get few, if any, fruits from your papaya tree due to excessive blossom drop. Keep the soil moist during the warm summer months and water frequently and deeply when temperatures rise into the 90s or higher.

When Cultural Practices Count

Fruit production peaks when papaya trees get 4 inches of rain monthly, but this amount may decrease with cooler weather. Water every other day for papayas grown in well-drained, sandy soils and once every three to four days for loamy soils. A lack of water may cause the blossoms to fall from the tree, even when temperatures are below 90 F. To conserve moisture in the soil, spread a 2- to 6-inch-deep layer of wood bark mulch around the plant, not closer than 8 inches to the trunk.

Water in one-quarter pound of ammonium sulfate 21-0-0 fertilizer monthly for the first six months after planting and use one-half pound each month after that. Switch to a balanced fertilizer that contains phosphorous if your papaya tree shows signs of deficiency, such as dark red colors on the stems or leaf veins accompanied with dark green foliage.